Barrier reef panic? – not so much

The Great Barrier Reef lies off the coast of Q...

The Great Barrier Reef lies off the coast of Queensland Image via Wikipedia

It seems that when you look at the way the data was gathered, and find that while some areas of the GBR declined, others gained. Analysed other ways, it doesn’t seem so alarming.

Perhaps the phrase is “coral picking”?

Assessing loss of coral cover on the Great Barrier Reef: A response to Hughes et al. (2011)

H. Sweatman and C. Syms


Hughes et al. (Coral Reefs, 2011, in press) challenge our interpretations of the changes in coral cover observed on the Great Barrier Reef (GBR) between 1986 and 2004 (Sweatman et al. in Coral Reefs 30:521–531, 2011). They question whether we can accurately assign all causes of coral loss; we contend that this makes no difference to the observed changes. They defend the validity of historical data on coral cover from before the start of systematic large-scale monitoring and conclude that coral cover has been declining since at least 1960, but we find no trend in the early data. We remain convinced that combining data collected at different spatial scales (quadrats and transects in the past mixed with more recent whole-reef averages from manta tows) are likely to overestimate decline, because whole-reef averages will very rarely reach the high cover values that can occur at the quadrat scale.

Hughes et al. (Coral Reefs, 2011, in press) state that we dismiss runoff as a cause of ecosystem degradation; we defend our interpretations and dispute some of their examples. In summary, we stand by our conclusion that coral cover on the GBR declined in the period 1986–2004 but through localised and unsynchronised changes that included recovery.

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37 thoughts on “Barrier reef panic? – not so much

  1. Corals depend on symbiotic algae for food. These algal species are sensitive to environmental changes so corals change them as and when required. Over the change period whitening occurs. An alarmist report a year or so back claimed GBR failures in one part due to higher temperatures. 6 months later that part of the GBR was back in business as a thriving reef. It was a period of symbiot change, for whatever reason. So corals seem to be able to sustain temperature changes it is the algae that are temperature sensitive.
    Corals of similar species as those of the GBR live quite happily in the Persian Gulf with much higher temperatures than those round the GBR.
    One thing that corals cannot stand is sea level falls. Rising sea levels are no problem as growth keeps up with the rises.

  2. corals have been around for hundreds of millions of years.
    I’m no scientist, but i guess they have experienced warmer and cooler climes before

  3. But, but Julia Gillard tells us the sea level is rising and the reef is in danger unless we apply a carbon tax compress…sarc.

  4. I first heard that the Great Barrier Reef was destroyed in the 1960s by being eaten by the Crown of Thorns seastar. (We called them starfish back then, but then someone realized that, by golly, they weren’t fish after all.) Perhaps someday my carbon footprint will become a carbon dioxide footprint, though I don’t know how to walk on CO2 unless it’s dry ice, and that sounds unhealthy.)
    Oh yeah. Then the GBR was destroyed again by pollution and runoff. And probably by fish (and seastars) not using the porta-johns.
    No one ever talks about it, but I imagine that none of the above matters because the reef must have been destroyed in the last ice age when the sea level dropped 100 meters. Maybe I’ll ask Bob Carter, he should know these things.
    I wonder what happened during the Medieval Warm Period and Roman Warm Periods. We know that polar bears must have gone extinct during both of those periods, which is why Gavin could’t find any on his recent trip to Churchill. Maybe those periods merely mortally wounded the coral critters.

  5. Whatever happened to the coral bleaching via “ocean acidification” theory? That didn’t work out so well, apparently. Now they’re trying a different tack. $cience with an agenda isn’t science at all. But, as long as they get their funding, that’s what is most important.

  6. John Marshall:
    Thanks for the clarification. It sounds like you are very familiar with this topic. Can you suggest an objective basic source of coral reefs that addresses the current issues of acidification?

  7. MangoChutney says:
    July 15, 2011 at 5:08 am
    “corals have been around for hundreds of millions of years.”
    Indeed. The oldest known coral reefs are in the Middle Ordovician about 470 million years ago. But taxanomic grounds, it appears that the Phylum Cnidaria which includes corals was probably the second major group of multicellular animals to evolve — after the sponges. That would likely be 550 million years ago or earlier. Corals have survived glaciations, meteor impacts, massive vulcanism, disease, predation and mass extinctions.
    The notion that they will not simply colonize poleward if oceans warm seems pretty weird. And the idea that they can not survive a bit of warming in most if not all of their current range doesn’t seem all that well found either. My opinion: the purported demise of corals is more likely the result of dubious science or possibly in some cases pollution than a lack of robustness wrt to modest climate change.

  8. current issues of acidification?Bernie says:
    July 15, 2011 at 5:30 am
    I,m not john:-)
    but the current issues are…bullsh*t
    and gillard is mouthing whats shes told, be so nice if she grew a brain and did her own research1

  9. Notes and Caloric Austrailia (Feed your talking points)
    About Fracking
    1) Visualize blueprints for the fracking platforms which include EPA water channels and treatment facilities :Assigning Enterprise rights for water management to the EPA preserves and likely promotes increases to land values*good for jobs..good for advancing caretaker environmental concerns.
    About the Conversion to Green Technology:
    1) Strong economy funds steady 100 year transition to green technology (which is not an economic engine. These are one dimensional economic products that are equivalent in utility to the economic momentum provided by lawn mowers, barbecue pits, air filters, etc) Bad economy increases the cost to green transition because it requires greater amounts of debt which devalues the purchasing power of currencies thus further eroding economic vitality..increases debt..increases costs
    2) Not economic engines: 1) Green tech replaces older economic units a) replacement costs impact economic diversity as functions of inflationary or deflationary value (1) Higher prices reduces purchasing opportunities…lower prices increase them (2)Think $10,000 dvd player to replace $100 VCR (3)Think Tax credits and other enterprise subsidies as components of total cost and inflationary impact (a) what economic impact will enforced transition to new generation marketplace units have upon value adding money supply growth? (Rhetorical..Is having!)
    About CO2:
    1) CO2 is plant food.
    2) Its concentration in the atmosphere is increasing because the strength of the magnetosphere (density) is increasing and thus causing all other atmospheric layers to contract (this contraction leads to cooling (Earth Radiative Budget Equation ERBE). We know that the magnetosphere is becoming denser because satellites have measured significant declines in the extent of the Ionosphere (Ions that are dispersed when the ejection of Solar Magnetic energy Protons strikes the magnetosphere. There is, thus, a correlation between Sunspot cycles and the strength of the Magnetosphere and the total height of the atmosphere and how much heat energy is radiated back into space. The magnetosphere also has its density increased by tectonic aerosols like SO2 (which global warmists intentionally misrepresent as reflecting infrared energy so that they can sell the paradigm of a closed, Earth Bound determined, climate system and that is the basis upon which they use public policy forums to increase their access to political power–which is about deciding how rights to whats are distributed)
    3) It is not possible for the concentration of CO2 to rise on earth when temperatures are also rising at lower levels of the atmosphere because these lower level temperature rises force the upper tropospheric response amplitude to expand *Warm weather processes also make more air molecules especially Water Vapor.
    4) CO2 increases until cooling air temperatures throughout the atmosphere force an Equilibration to rate of CO2 absorption by cooling the oceans, its primary sink
    5) Coriolis forces are also an important determinant of change in ocean temperatures. Their influence is greatest when the gravitational relationship between Earth and Sun is driven by fluctuations of the energy density of the sun’s core as determined by the variations to Gauss strength that the sun encounters during its Galactic orbit. A denser sun keeps more weight thus leading to an increase to its gravitational impacts upon the solar system.
    Earth’s first responds to the increasing gravitational impact of the sun with measurable changes to its axial tilt and rate of wobbles (Obliquity). Much like a liquid made to swirl around the inside of container whose movement is directed by outside forces, Earth attempts to compensate for apparent changes to volume and weight by increasing the counterbalancing rate of movement of its liquids. At the poles, and as is occurring now, this entails:
    (1) increasing the rate that cold water moves to lower latitudes along continental flow channels
    (a) see back to 1996 and consider solar cycles
    (a1) Also watch the Caloric surface heat reflection of the Great Pacific Garbage Patch expand and contract in tune with seasonality’s impact upon its Oceanic circulation gyre.
    (a1a) maybe by volume it is the size of Rhode Island, but it is a Caloric Austrailia when the summer sun is overhead.
    (a1b) When the Great Pacific Garbage Patch exhibits itself as a Caloric Austrailia it has a significantly greater impact upon the native potential completeness of the Pacific Ocean’s carbon sequestration cycle (ocean acidification/alkalinity changes)
    (2) more high latitude volcanic activity
    (b) *
    CO2 saturation is a false dilemma.
    1) Yes CO2 is a greenhouse gas, but Greenhouse Gases do not control the directionality and convective flow rates of Infrared Energy. They are controlled by atmospheric pressure which is a product of Ocean Temperatures and Magnetic forces acting upon atmospheric height potentials.

  10. You all better get up there and see the Great Barrier Reef quick. At this rate it may only be there for another million years or so.

  11. ozspeaksup:
    My suspicion is that you are correct but I would just like a more formal scientific, data-based assessment of the issue or non-issue.

  12. One neat thing about the web is that you can, after a bit of searching, actually talk to people who live on the Great Barrier Reef. Back when the OMG-the-reef-is-dieing hysteria first hit the papers I was bumbling about the web, trying to learn more about the Great Barrier Reef, and accidentally wound up at the site of some tour guide who led scuba tours.
    One thing about such tour guides is that they are not out to lose customers. So they sort of feel you out to find out if you are a green whack-job. If you are they will nod their heads up and down and be agreeable, because they don’t want to lose your business. However even then they will tell you they know where there are untouched reefs, unblanched by bleaching, because they want you to come on their tour.
    Of course, if they find out you’re some nosey guy on the far side of the planet who hasn’t got any money, they might get a bit rude, especially if they are busy. However other times they are just kicking back with one of those big Australian beers, and they sort of like talking to someone they don’t have to be polite to, because they aren’t a customer.
    That’s when you learn what is really happening out on the reefs, and that the media is full of bunkum.
    I think it sad that the media has become so slanted that it is lieing down, (on the job.) I think it is great that we ourselves can be the reporters, and interview people on the far side of the planet, via the web.

  13. Bernie says:
    July 15, 2011 at 5:30 am
    Can you suggest an objective basic source of coral reefs that addresses the current issues of acidification?
    Look at the paleo records for past 100 million years, for CO2 levels and ocean Ph as widely available on the internet. What you will find is that in the past, except for the last few million years, the oceans have consistently been more acidic than they are now and CO2 levels were also much higher.
    So the question is, for tens of millions of years prior to the current ice ages, CO2 levels were higher and the oceans were more acidic, so how did the corals survive? How if CO2 and “acidification” is a problem today, why was it not a problem for tens of millions of years? Is it not more likely that a return to past conditions, the conditions in which corals had tens of millions or years of evolution, is it not more likely that this will be a net benefit to corals.
    Currently corals are mostly limited to growing in the tropics, largely because they do not do well in cold water. So, isn’t warming of the oceans more likely to benefit corals by increasing their habitats? We now know that “coral bleaching” is not permanent, that it reflects a natural process whereby one species of polyps replaces another as local conditions change.
    Thus, it seems more likely that projected changes due to AGW will be a net benefit to corals and the panic reflects a lack of understanding of the past and the nature of corals. The major threat to coral is sedimentation from land use change. Covering a reef with mud does kill it, as clearly demonstrated in the Malacca straights over the past 30 years as a result of large scale deforestation. CO2 and acidification does not harm reefs, as demonstrated by millions of years of geological records.

  14. Look at page 56 of this reference
    You will see that for the past 100 million years the oceans have been much more acidic than now and CO2 levels much higher. How did the corals survive?
    You will also see that for the past 10 million years the oceans have been “acidifying”. This is quite obviously a natural process that some humans are trying to take credit for. Like Al Gore inventing the internet, someone notices that the oceans are “acidifying” and jump to the conclusion that humans are the case. Without first considering that just maybe it has been going on for a lot longer than humans have been releasing CO2 from fossil fuels.
    In any case, the correct scientific term (chemistry) for reducing the Ph of the oceans from 8.2 by adding CO2 is NEUTRALIZATION. Climate science calls it “acidification” to create panic and alarm. You cannot acidify the oceans (a base) until the Ph reaches 7.0, which will never happen even if we burned all fossil fuels on the planet.
    A buffered solution like the oceans resists changing from a base to an acid, as you must first force the buffer out of solution. The large deposits of limestone for example show how difficult it is for CO2 to acidify the oceans. It is the oceans than are decarboning the atmosphere, through the formation of limestone. If we wanted to acidify the oceans through CO2, you would need to also burn all the limestone on the planet (we do this now to form cement), and even then it is doubtful it would work, as the calcium would find its way back into the oceans through erosion and weathering.

  15. Fascinating to hear that 6 month bleaching is quite possibly a condo-swap for the symbiots looking for more comfortable digs. That certainly is a hysterical announcement just waiting to happen. Wow. Just think of the possiblities!
    How to create a great, can’t-fail-to-inspire GBR Disaster Story:
    Map out an accessible portion of the reef and number each of 100 zones. When and as temperature rises and the symbiots vacate, you mark that area RED on the map and blame global warming for killing the corals. When some other areas cool and the same happens, mark them RED on the map and blame ocean acidification for killing the corals. Foresee shell-less clams. In other areas, attacks by predators create new opporunities to mark the area RED and blame the death of corals on a loss of biodiversity or pollution or over-touristing or shifting monsoons or prayer in school. Be imaginative but don’t stray too far from the main memes. After a few years of intensive research the map will be more than half red.
    Issue an alarmist call about the reef being extinct in 100 years because of mankind’s perfidy in our relationship with Mother Nature (etc) and wave the numbered, reddened map around for all to see. Provide a numbered list and the Death Date you noted for each zone. Scream ‘denier!’ at anyone who wants to revisit and of the RED map sites to check on your work. Issue a suppplementary ‘projection’ of the reddening and declare that the death spiral of the Great Barrier Reef has already been going on since industrialisation poisoned the atmosphere with CO2. Weep slightly but keep a stiff upper lip while saying, “Nemo” in a stage whisper.
    Write an alarmist article with the red-zoned map prominently featured and have it reviewed by some pals for spelling. Don’t forget to [ask for money to study the problem/indicate important areas for future research]. Ask your pals to recommend the article for inclusion in AR5. Delete the email.
    A gravy train is all about the trip, not the destination.

  16. Andy Adkins says:
    July 15, 2011 at 7:04 am
    …5) Coriolis forces are also an important determinant of change in ocean temperatures. Their influence is greatest when the gravitational relationship between Earth and Sun is driven by fluctuations of the energy density of the sun’s core as determined by the variations to Gauss strength that the sun encounters during its Galactic orbit. A denser sun keeps more weight thus leading to an increase to its gravitational impacts upon the solar system

    Mmmm, not so sure about that. The sun’s gravitational effects are a function of its mass. If you were within a few sun diameters of the surface of the sun a change in its diamter might have an effect on the orbital mechanics of a circling object with sun mass constant since you might get a few percentage points change in the near gravitational field gradient. However, on a solar system scale with gravitational effects in proportion to 1/r^2, the sun is effectively a point mass for all intents and purposes. No change in mass, no change in “gravitational impacts”.

  17. Symbiot-D is a high-temperature algae. It is not common everywhere, just in the warmest waters. But it’s been found at different reefs throughout the world in different levels of reef penetration. It does seem that it takes some time for the corals to starve and on one algae before the Symbiot-D variety can move in.
    Meanwhile I do caution on the nutrification problem. It does increase coral predators like the spiny starfish, as well as jellies.

  18. MangoChutney says:
    July 15, 2011 at 5:08 am
    “corals have been around for hundreds of millions of years.
    I’m no scientist, but i guess they have experienced warmer and cooler climes before
    Yes my dear mango, but not sticky fingers from a thousands of greenpeazers on vacation, err doing research.

  19. DJ Hawkins
    The mass of the sun is only equationally constant when time=0,
    See “Time Dependent Photon Transport in a Three Dimensional Interstellar Cloud with Stochastic Clumps”
    Belleni-Morante, Aldo; Saccomandi, Giuseppe
    Astrophysics and Space Science, Volume 234, Issue 1, pp.85-105
    ….We consider time dependent photon transport in a three dimensional interstellar cloud which occupies a three dimensional regionV. One or more clumps of given shapes are present withinV and their positions are determined by a suitable set of stochastic variables. Iff is the photon number density in the cloud or in the clumps, then our mathematical model leads to two coupled initial value problems for the average photon density over the stochastic variables and forf * =f -. By using the theory of semigroups, we prove existence and uniqueness of a strongly continuous solution and examine the small fluctuation approximation of such a solution.
    1) The sun’s energy management is modulated by its location in the milky way. If it is located within one of the galactic rings then it encounters a regular variability in the amount of gravitational density that it encounters (it is travelling through magnetic fields most of which are interstellar clouds that are considered to be the products of supernovae**understand the term Gauss**). This variability of gravitational (magnetic field) density determines how the sun manages its energy production. During the first ~10,000 year period when the sun is in the dense environment of the Interstellar cloud, the pressure imposed upon it forces greater energy production…the earth warms to an interglacial maximum, because increased energy production by the sun correlates with an increase to and strengthening of its releases of magnetically charged ions some of which eventually interact with the earth’s magnetosphere causing it to weaken and thus allowing the upper tropospheric response amplitude to increase (this determines earth’s temperature grabbing a thicker blanket)
    2) True Milankovitch event—the sun’s 100,000 year eyewall replacement cycle (convenient imagery): the sun’s core loses electrons? (subatomic particles) to its outer layers and the shifting balance of their “weight”/ energy potential determine how efficiently the sun is able to share its energy within the heliosheath. When it is less efficient, the sun becomes more massive; its gravity then bends the orbits of solar bodies, increases tectonic activity and mountain building 1)The Sun’s sunspot grand maxima (~700 years) time scale math is saying that the current Solar Minimum will be greater than the little Ice Age (maunder minimum) so long as the sun is still undergoing the same Milankovitch 100,000 year eyewall replacement cycle.
    a) ** We can have a better understanding of the internal dynamo of the sun’s energy fusion process if we discarded consideration of gleissenberg cycles, counted the dalton minimum as a feature to the maunder minimum, and used only the grand maximums to mark start/ end points of the sun’s energy process
    3) If we are charting the effect of solar energy management upon earth’s climate, then even wiki established fact that over the last 10000 years the warm periods are growing less warm and the cold periods are growing colder means that the sun has been increasing the amount of energy that it is keeping in cycles that accord with its energy fusion dynamo (It is formulaic but our life spans and accumulated scientific data will be too inadequate to certify for 100,000 years-we have to record all the related data changes for the period)
    a) the 4 recorded gleissenberg cycles are out of tune manmade distinction identified because of how close we are standing to all recorded data. In the warmest heart of the Milankovitch 100,000 year eyewall replacement cycle, where the sun is most efficient, I expect that the 11 year sunspot cycle and gleissenberg cycles are not distiguishable. INSTEAD THEIR CURRENT DETECTABILITY IS SYMPTOMATIC OF HOW FAR ALONG INTO THE INEFFICIENCY OF THE SUN’S ENERGY FUSION DYNAMO WE Are***compare (Katayama & Sato, 2000
    4) Suffice it to say, the occurrence of the little ice age, lasting nearly 400 years based upon the cycle of minimums recorded, is clear indication that the sun has exhausted its capacity to direct its energy management as a result the sun is now being bullied by its presence within the interstellar cloud. Yes we have warmed since 1850 but this more likely indicates that we entered into denser portions of the interstellar cloud.

  20. DJ Hawkins (more notes on what well cited investigations suggest)
    1. The processes of the 100,000 year Malinkovitch event are essentially like a hurricane’s eyewall replacement cycle; the strengthening of the outer bands blocks the inflow of energy to the center
    (a) Van der Waals forces disperse electrons beyond their capacity to affect the radiative influence of the sun’s plasma conveyor belt.
    (1) the processes of the malinkovitch event when timelined according to known solar maximums are ~700 years in length, but it is likely that at true Malinkovitch efficiency the differentiation of Maxes requires considerably longer time scales
    2. As the most energetic aspects move away from the core energy dispersal mechanism, that mechanism experiences a decline in its ability to move energy, but not the loss of its ability to produce energy so its energy inefficiency contributes to the net energy body’s increase in mass.
    (a) The little ice age.
    3. As energy mass accumulates, net gravity increases and corresponds with an increase in the strength of the Lorentz force determining the rate at which gravity is able to reintergrate the most energetic aspects of the energy body into its energy production core; their ability to be reintegrated into the original center is lessened by gravity’s thickness (this is the Lorentz force and it spirally repeats from solar center to the outer edges of the heliosheath)
    (a) the reintergration of energy that gradually attempted to feed greater sun energy productivity probably occurred during the Dalton phase of the Maunder Minimum
    (1) The sun’s failure to restart a so called “warmer” gleissenberg cycle was the result of the energy body’s gravity determined Lorentz forces.
    (b) The carrington event symbolized: 1) the sun capturing enough energy with its core to produce the refiring of the magnetic polarities responsible for the streaming of its plasma conveyor belt to the solar Malinkovitch period’s equational potential 2) that the magnetic environment encountered by the Heliosphere unleashed an eclipse of the total Lorentz force was eclipsed 3) The last 150 years of sunspot activity has been the result of energy splash back onto surface layers of the sun that has been sufficient to maintain the advantage of sunspot potential and the magnetic environment encountered by the heliosphere over the total Lorentz force that provokes solar energy management.

  21. DJ Hawkins says
    If you were within a few sun diameters of the surface of the sun a change in its diamter might have an effect on the orbital mechanics of a circling object with sun mass constant since you might get a few percentage points change in the near gravitational field gradient.
    There is no “might” about this. You certainly will not get any percentage points change. This applies right down to the surface of the sun.
    And you got cranked.

  22. Andy Adkins’ reply, although weird, is earnest and probably heart-felt. However, I tend to ageee with John Marshall that the past tends to predict the future. Speaking as a Floridian who lives on a highly developed ancient coral reef, I tend to consider reefs as earthworks. Natural uprisings, tides and currents build earthworks that become habitats for plants, corals and other organism that in turn evolve a habitat ultimately upon which we’re growing orange or pecan trees and planning a trips to the Bahamas.
    Here in Florida, though, we sink ships to make coral reefs. We’re fairly certain that any ship we sink will become a reef where well endowed ($$$) tourists may experience the wonders and hosing administered by the uneducated classes who fortuitously school themselves in the black arts of aquaculture, navigation and accounting.
    The notion that the GREAT BARRIER REEF! could be in some way be eroded or impacted by something I DID through a contribution to GLOBAL WARMING is STUPID!

  23. “Ric Werme says:
    July 15, 2011 at 5:13 am
    I first heard that the Great Barrier Reef was destroyed in the 1960s by being eaten by the Crown of Thorns seastar. (We called them starfish back then, but then someone realized that, by golly, they weren’t fish after all.) Perhaps someday my carbon footprint will become a carbon dioxide footprint, though I don’t know how to walk on CO2 unless it’s dry ice, and that sounds unhealthy.)”
    FWIW: 🙂
    Before returning to NZ I had my early schooling in OZ.
    In the early 1970s we were taught told in school while in OZ. The Crown of Thorns starfish were eating the GBR alive and it was unlikely to be a coral reef left in 20yrs time. That conclusion BTW came from just one Marine biologist come activist!

  24. just another excuse for those cranberrians (Bob and Julia) to scream the sky if falling. Bob is also screaming the koala’s are dying and humans are responsible…… can someone tape his mouth shut please!

  25. LazyTeenager says:
    July 15, 2011 at 5:52 pm
    DJ Hawkins says
    If you were within a few sun diameters of the surface of the sun a change in its diamter might have an effect on the orbital mechanics of a circling object with sun mass constant since you might get a few percentage points change in the near gravitational field gradient.
    There is no “might” about this. You certainly will not get any percentage points change. This applies right down to the surface of the sun.
    And you got cranked.

    You do live up to your handle. You might note that the adults were discussing the potential change in the sun’s solar system-wide gravitational effects with a change in stellar density. Classic Newtonian physics treats gravitational interactions as affecting point masses. This is true for spherical masses of constant density. Deviations occur for very large masses or very small distances which require the use of Einstein’s Theory of General Relativity. I freely admit I don’t have the math skills to exactly calculate the difference. However if Andy Adkins were remotely correct in his claim (which he doesn’t defend in his reply, however fascinating it is) then earth’s orbital period would be affected by changes in the solar density. It isn’t. Crank you.

  26. Andy Adkins says:
    July 15, 2011 at 3:10 pm
    My apologies to those commentators who are enduring these display half-done and poorly edited thought exercises
    Thanks for finally remembering that we were discussing coral reefs, not interstellar physics. On a stylistic note: please edit your work with an eye toward avoiding anthropomorphic attribution as in “Earth attempts to compensate…”. The earth doesn’t think.

  27. zooxanthellae don’t feed the corals, they supplement the corals while benefiting from the corals metabolic CO2 output. It is hard to conclude that elevated CO2 is killing algae that utilize it as food. Corals are nocturnal plankton feeders that hide from the heat and light of the day by contracting inside of their colonial exoskeletons. In these papers I never see any consideration for the fact that on a reef face where most of the corals live, the temperatures are vertically stratified. Temperatures also cycle diurnally. The temperature declines as you plunge into the deeper water. The corals peter out when there is not enough light to sustain the zooxanthellae. I have a hard time attributing bleaching to temperature. There are too many other independent variables that are more likely candidates.

  28. Ferd Berple
    Thanks for the reference. I can’t say I understood much of it, but clearly Zeebe is making a strong case that one way to reconcile a troublesome low SST for the Cretaceous period using O18/O16 ratio is to factor in a more acidic shallow seas (lower pH) resulting in heavier shells for various florsminifer – which presumably indicates a subsequent viable environment for many kinds of coral, etc. Please let me know if I have missed the point you were making with the reference.

  29. Important bits considering the future of coral REEFS: even that corals have inhabit the Earth for millions of years, corals reef have not been the dominated form of reef structure for most of this time. Corals found in the GBR can live under warmer conditions (as in the Red Sea) but populations are adapted to their specific environment, corals in the GBR are not adapted to live in extremely warm environments. If it is the symbiont who is affected by temperature changes, the coral host, or both is still a matter of discussion, but nevertheless when it gets really hot in the GBR corals bleach and die. During 1998 calcification in inshore corals dropped to remarkably low levels and it took the corals 2-3 years to recover. Of course populations can adapt, but only if changes occur at a rate that allows the organisms to respond.
    The threat for the GBR at the moment is mainly for inshore corals, and this where part of the confusion arises, mid-shelf and offshore reefs are doing some how well. When assessing the health of the GBR it is important to notice the difference cross-shelf and north to south differences. The GBR is a HUGE coral reef system that includes very different environmental settings and this should always be taken into consideration. In the inshore area there is an amplification of environmental changes (e.g. temperature variability) and added to this there is extra pressure from terrestrial run-off. Changes in the sediment and nutrient supply to the reef are probably the biggest threat. Furthermore when you have multiple stressors the tolerance level of an organism usually drops, so turbidity, eutrophycation, global warming and ocean acidification will probably synergistically, something that not necessarily has happened before in the GBR. Ocean acidification is a process that cannot be argued as it is simple chemistry, the impact on marine calcifiers is no clear but most experimental studies show negative changes in calcification, and apparently after a threshold level is crossed calcification stops. This could be similar to what is found with temperature, corals can only tolerate a range of temperature once values cross a thermal maximum calcification stops.
    Apparently what is happening in the inshore is a community change, algae and phtyoplankton has become more dominant while coral cover and health has declined. The problem is that the degradation of the inshore are could progressively affect the mid-shelf and offshore area, as for example the carbon chemistry of the reef lagoon is very susceptible to biological driven changes. Furthermore if temperature continue to increase the thermal maximum for mid-shelf corals could be crossed and bleaching will become a problem in other reef areas not yet being affected.

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